SEOUL, Oct. 11 (Yonhap) -- Nuclear envoys from South Korea, the United States and Japan will hold trilateral talks in Tokyo next week to discuss North Korean nuclear issues, a Seoul official said Thursday.

Lim Sung-nam, Seoul's chief envoy to the six-party talks on ending the North's nuclear weapons program, will hold talks with his U.S. and Japanese counterparts, Glyn Davies and Shinsuke Sugiyama, next Wednesday, the foreign ministry official said.

The official, who spoke on the condition of anonymity, said the nuclear envoys "will jointly assess the current situation with the North Korean nuclear issues and discuss ways to maintain stability on the Korean Peninsula."

The three-way talks come amid reports of progress in the North's light-water reactor project that experts say may help expand the North's nuclear weapons capacity.

Last month, Lim visited Beijing and held talks with his Chinese counterpart Wu Dawei. During the Beijing talks, the two sides agreed to keep a "close watch" on progress in the North's light-water atomic reactor project, Seoul officials said.

South Korea is concerned that the North's reactor that is under construction at its main nuclear complex in Yongbyon might be a cover to stockpile enriched uranium, a fissile material used to make bombs, although Pyongyang claims it is for producing electricity.

The International Atomic Energy Agency has said North Korea has made "significant" progress in the light-water reactor project. Citing satellite imagery, the U.N. said the North has put a dome over the facility.

The six-party talks, which involve the two Koreas, the United States, China, Russia and Japan, have been dormant since late 2008.

After the trilateral talks in Tokyo, the U.S. envoy will make a three-day visit to South Korea from Oct. 18, Seoul's foreign ministry spokesman Cho Tai-young told reporters.

Davies plans to visit Seoul as part of his regional trip to Northeast Asia, including China, Cho said.

Meanwhile, First Vice Foreign Minister Ahn Ho-young and U.S. Deputy Secretary of State William Burns will hold a fourth round of vice ministerial meetings in Seoul on Tuesday to discuss a range of bilateral issues, including North Korea, Cho said.

North Korea has stepped up its harsh rhetoric against South Korea and the U.S. after Seoul announced on Sunday that it has signed a new arms deal with Washington under which it can extend the range of its missiles from the present 300 kilometers to 800 kilometers, far enough to strike any part of its northern communist neighbor.